Whey protein is a rich source of naturally occurring branched chain amino acids, which are important for those who have an active lifestyle. The body requires higher amounts of these amino acids during and after exercise because they quickly become in high demand throughout the body. Low BCAA levels contribute to fatigue and should be replaced in one hour or less. A 2009 study at McMaster University in Ontario, Canada found that, despite being at rest, subjects who consumed whey had nine times greater muscle repair and growth than those who ate other types of protein (casein and soy). After exercise, the same whey group saw a 122 percent greater muscle protein synthesis compared to the casein group and 31 percent greater than the soy group.
West, D. American Journal of Clinical Nutrition, September 2011: vol 94: pp 795-803.Pasiakos, S. American Journal of Clinical Nutrition, September 2011
